Gardnerella vaginalis

Gardnerella
Microscopic picture of vaginal epithelial clue cells coated with Gardnerella vaginalis, magnified 400 times.
Scientific classification
Kingdom:	Bacteria
Phylum:	Actinobacteria
Class:	Actinobacteria
Order:	Bifidobacteriales
Family:	Bifidobacteriaceae
Genus:	Gardnerella
Species:	G. vaginalis
Binomial name
Gardnerella vaginalis (Gardner and Dukes 1955) Greenwood and Pickett 1980

Gardnerella is a genus of Gram-variable-staining facultative anaerobic bacteria of which G. vaginalis is the only species.

Once classified as Haemophilus vaginalis and afterwards as Corynebacterium vaginalis, Gardnerella vaginalis grows as small, circular, convex, gray colonies on chocolate agar; it also grows on HBT agar. A selective medium for G. vaginalis is colistin-oxolinic acid blood agar.

Clinical significance

Gardnerella vaginalis is a facultatively anaerobic Gram-variable rod that can cause bacterial vaginosis in some women as a result of a disruption in the normal vaginal microflora. The resident anaerobic Lactobacillus population in the vagina are responsible for the acidic environment. Once the anaerobes have supplanted the normal vaginal bacteria, prescription antibiotics with anaerobic coverage may have to be given to eliminate the G. vaginalis and allow the balance to be restored.

While typically isolated in genital cultures, it may also be detected in other samples from blood, urine, and pharynx. G. vaginalis is sexually transmitted. Although G. vaginalis is a major species present in bacterial vaginosis, it can also be isolated from women without any signs or symptoms of infection.

It has a Gram-positive cell wall, but because the cell wall is so thin it can appear either Gram-positive or Gram-negative under the microscope. It is associated microscopically with clue cells, which are epithelial cells covered in bacteria. G. vaginalis produces a pore-forming toxin, vaginolysin, which affects only human cells.

Protease and sialidase enzyme activities frequently accompany G. vaginalis.

Treatment

One method of antibiotic treatment is metronidazole.

The effectiveness of treating bacterial vaginosis with antibiotics is well-documented.

Symptoms

Gardnerella vaginalis may be associated with a condition called bacterial vaginosis, whose symtoms include vaginal discharge, vaginal irritation, and a "fish like" odor. In the "amine whiff test" 10% KOH is added to the discharge, a positive result indicated if a fishy smell is produced. This and other tests can be used to distinguish between vaginal symptoms related to G. vaginalis from those caused by other organisms, such as Trichomonas and Candida albicans, which are similar and may require different treatment. Trichomonas vaginalis and Gardnerella vaginalis have similar clinical presentations and can cause a frothy gray or yellow-green vaginal discharge, pruritis, and produce a positive "whiff-test." The two can be distinguished using a wet mount slide, where a swab of the vaginal epithelium is diluted and then placed onto a slide for observation under a microscope. Gardnerella reveals a classic "clue cell" under the microscope, showing bacteria adhering to the surface of squamous epithelial cells. Both conditions are treated with metronidazole.

External links

• MeSH Gardnerella